Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first animated image in a sequence of a display screen or portion thereof with a graphical user interface, showing the new design.

FIG. 2 is a front view of a second animated image thereof.

FIG. 3 is a front view of a third animated image thereof.

FIG. 4 is a front view of a fourth animated image thereof; and,

FIG. 5 is a front view of a fifth animated image thereof.

The broken lines show a display screen or portion thereof and form no part of the claimed design.

The appearance of the image sequentially transitions between the images shown in FIGS. 1 through 5. The process or period in which one image transitions to another forms no part of the claimed design.

In all of the figures, areas of the design shown in a solid fill illustrate a visual contrast compared to the corresponding non-filled areas. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 